LR4 is a three-way crossover under voltage control. Two four-pole state variable filters in series allow an input signal to be split into three non-overlapping bands, while the fourth-order Linkwitz-Riley slopes provide ideal band separation. And because both filters are full range, the bandwidths are arbitrary, not range-restricted.
https://www.youtube.com/watch?v=fXJPYUYkP9M